1. Field of the Invention
The present invention relates to a III-nitride semiconductor laser device, and a method of fabricating the III-nitride semiconductor laser device.
2. Related Background Art
Patent Literature 1 discloses a laser device. When a primary surface of a substrate is a face inclined at 28.1 degrees from a {0001} plane toward a direction equivalent to the [1-100] direction, secondary cleaved facets are {11-20} planes perpendicular to both of the primary surface and optical cavity faces, and the laser device is of a rectangular parallelepiped shape.
Patent Literature 2 discloses a nitride semiconductor device. The back surface of the substrate for cleavage is polished to reduce the total thickness to about 100 μm. A dielectric multilayer film is deposited on cleaved facets.
Patent Literature 3 discloses a nitride-based compound semiconductor device. The substrate used for the nitride-based compound semiconductor device is comprised of a nitride-based compound semiconductor with the threading dislocation density of not more than 3×106 cm−2 and the in-plane threading dislocation density is substantially uniform.
Patent Literature 4 discloses a nitride-based semiconductor laser device. In the nitride-based semiconductor laser device, cleaved facets are formed as described below. With respect to recesses which are made by etching from layers for the semiconductor laser device to an n-type GaN substrate, scribed grooves are formed using a laser scriber and arranged like a dashed line (at intervals of about 40 μm) in a direction orthogonal to an extending direction of ridge portions, while avoiding projections made during the etching of cavity faces on the n-type GaN substrate. Then the wafer is cleaved at positions of the scribed grooves. On this occasion, each of regions without the scribed grooves, e.g., each projection, is cleaved from the adjacent scribed groove as an origin. As a result, device separation faces are formed as a cleaved facet of a (0001) plane of the n-type GaN substrate.
Patent Literature 5 discloses a light emitting device. The light emitting device is able to readily emit light at a long wavelength, without deterioration of luminous efficiency in its light emitting layer.
Patent Literature 6 discloses a nitride semiconductor device of an opposed electrode structure with reduced contact resistance. A nitride semiconductor substrate has first and second primary surfaces. The nitride semiconductor substrate includes a region whose crystal growth surface of a (0001) plane. A nitride semiconductor layer is grown on the first primary surface of the nitride semiconductor substrate. Grooves are formed in a second region of the second primary surface. The device has a stripe of a ridge shape above the first primary surface of the nitride semiconductor substrate. An optical cavity is produced by cleavage.
Non-patent Literature 1 discloses a semiconductor laser, formed on a semipolar (10-11) plane, in which a waveguide extends in an off-axis direction and in which mirrors for an optical cavity are made by reactive ion etching.    Patent Literature 1: Japanese Patent Application Laid-open No. 2001-230497    Patent Literature 2: Japanese Patent Application Laid-open No. 2005-353690    Patent Literature 3: Japanese Patent Application Laid-open No. 2007-184353    Patent Literature 4: Japanese Patent Application Laid-open No. 2009-081336    Patent Literature 5: Japanese Patent Application Laid-open No. 2008-235804    Patent Literature 6: Japanese Patent Application Laid-open No. 2005-159278    Non-patent Literature 1: Jpn. J. Appl. Phys. Vol. 46, No. 19, (2007) L444